How to remove all BLOCKED called in iPhone

How can I delete all BLOCKED calls on my iphone? Why isn't there a SELECT ALL capability? Thanks to Robo Calls...I've had to block hundreds of numbers. I finally had to get a new Cell Phone number, and the list of blocked numbers transferred from my old phone to my new phone when I used the RESTORE FROM BACKUP option when setting up my new phone. Robo-Calls are killing the Cell Phone industry. Editing one-by-one is unacceptable...as I have literally 400-500 blocked numbers. If Apple has not considered an easy way to fix this...I suggest they add a SELECT ALL button into their next release.